<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .wrap{
            display: flex;
            width: 400px;
            height: 400px;
            border: 1px solid;

            /*决定主轴是哪一根 以及 主轴的方向*/
            /*决定侧轴是哪一根 以及 侧轴的方向*/
            /*flex-direction: row;
            flex-wrap: wrap-reverse;*/
            flex-flow: row nowrap;

            /*主轴的富裕空间管理*/
            justify-content: space-between;
            /*侧轴的富裕空间管理*/
            align-items: flex-end;
            align-content: center;

        }
        .item{
            width: 50px;
            height: 50px;
            background: pink;
            font-size: 13px;
            line-height: 50px;
            text-align: center;
            border: 1px solid;
            box-sizing: border-box;
        }
    </style>
</head>
<body>
  <div class="wrap">
      <div class="item">1</div>
      <div class="item">2</div>
      <div class="item">3</div>
      <div class="item">4</div>
      <div class="item">5</div>
      <div class="item">6</div>
      <div class="item">7</div>
      <div class="item">8</div>
      <div class="item">9</div>
  </div>
</body>
</html>